Method of forming a finFET and structure

Abstract

A method for processing a substrate comprising at least a buried oxide (BOX) layer and a semiconductor material layer is provided. The method includes etching the semiconductor material layer to form a vertical semiconductor material structure overlying the BOX layer, leaving an exposed portion of the BOX layer. The method further includes exposing a top surface of the exposed portion of the BOX layer to an oxide etch resistant species to form a thin oxide etch resistant layer overlying the exposed portion of the BOX layer.

1. A method for processing a substrate comprising at least a buried oxide (BOX) layer and a semiconductor material layer, the method comprising:
 etching the semiconductor material layer to form a vertical semiconductor material structure overlying the BOX layer in a manner that avoids undercutting the vertical semiconductor material structure, leaving an exposed portion of the BOX layer; 
 prior to applying an etchant to the BOX layer that is capable of etching the BOX after the step of etching, exposing a top surface of the exposed portion of the BOX layer to an oxide etch resistant species to form a thin oxide etch resistant layer overlying the exposed portion of the BOX layer; and 
 thinning the vertical semiconductor material structure to form a thinned vertical structure so that the thin oxide etch resistant layer is adjacent to but not under any portion of the thinned vertical structure. 
 
     
     
       2. The method of  claim 1  further comprising:
 forming a hard mask layer overlying the semiconductor material layer; 
 forming a patterned photo resist layer overlying the hard mask layer; and 
 using the patterned photo resist layer etching the hard mask layer to form a hard mask. 
 
     
     
       3. The method of  claim 2 , wherein etching the semiconductor material layer comprises using the hard mask to form the vertical semiconductor material structure overlying the BOX layer. 
     
     
       4. The method of  claim 1 , wherein the step of etching comprising applying HBr. 
     
     
       5. The method of  claim 1 , wherein the oxide etch resistant layer includes Nitrogen. 
     
     
       6. The method of  claim 1 , wherein the exposing step includes exposing the exposed portion of the BOX layer to Nitrogen in a radio frequency plasma chamber. 
     
     
       7. The method of  claim 1 , wherein the exposing step includes using a decoupled plasma nitridation (DPN) process to expose the exposed portion of the BOX layer to Nitrogen. 
     
     
       8. The method of  claim 1  wherein the step of thinning comprises:
 after the step of exposing, growing a sacrificial oxide layer on at least an exposed surface of the vertical semiconductor material structure; and 
 performing a hydro-fluoride (HF) clean to substantially remove the sacrificial oxide layer, wherein the thin oxide etch resistant layer protects the exposed portion of the BOX layer from the HF clean. 
 
     
     
       9. The method of  claim 1 , wherein the exposing step is performed in a manner such that the thin oxide etch resistant layer has a thickness of less than 20 nanometers. 
     
     
       10. The method of  claim 9 , wherein the exposing step is performed in a manner such that the thin oxide etch resistant layer has a Nitrogen concentration profile such that a top portion of the thin oxide etch resistant layer has a significantly higher concentration of Nitrogen than a bottom portion of the thin oxide etch resistant layer. 
     
     
       11. The method of  claim 1 , wherein the exposing step is performed in a manner such that the thin oxide etch resistant layer has sufficient thickness to protect the underlying BOX layer from erosion caused by a subsequent wet cleaning steps. 
     
     
       12. A method for processing a substrate comprising at least a buried oxide (BOX) layer and a semiconductor material layer, the method comprising:
 forming a hard mask layer overlying the semiconductor material layer; 
 forming a patterned photo resist layer overlying the hard mask layer; 
 using the patterned photo resist layer, etching the hard mask layer to form a hard mask; 
 etching the semiconductor material layer using HBr, except for a portion of the semiconductor material layer underlying the hard mask to form a vertical semiconductor material structure overlying the BOX layer, leaving an exposed portion of the BOX layer; 
 prior to applying an etchant to the BOX that is capable of etching the BOX after the step of etching, exposing a top surface of the exposed portion of the BOX layer to Nitrogen to form a thin oxide etch resistant layer overlying the exposed portion of the BOX layer; 
 growing a sacrificial oxide layer on at least an exposed surface of the vertical semiconductor material structure; and 
 performing a hydro-fluoride (HF) clean to substantially remove the sacrificial oxide layer to form a thinned vertical structure, wherein the thin oxide etch resistant layer protects the exposed portion of the BOX layer from the HF clean and so that the thin oxide resistant layer is adjacent to but not under any portion of the thinned vertical structure. 
 
     
     
       13. The method of  claim 12 , wherein the vertical semiconductor material structure is a fin structure corresponding to a FinFET transistor. 
     
     
       14. The method of  claim 12 , wherein the exposing step includes exposing the exposed portion of the BOX layer to Nitrogen in a radio frequency plasma chamber. 
     
     
       15. The method of  claim 12 , wherein the exposing step includes using a decoupled plasma nitridation (DPN) process to expose the exposed portion of the BOX layer to Nitrogen. 
     
     
       16. The method of  claim 12 , wherein the exposing step is performed in a manner such that the thin oxide etch resistant layer has a thickness of less than 20 nanometers. 
     
     
       17. The method of  claim 16 , wherein the exposing step is performed in a manner such that the thin oxide etch resistant layer has a Nitrogen density concentration such that a top portion of the thin oxide etch resistant layer has a significantly higher concentration of Nitrogen than a bottom portion of the thin oxide etch resistant layer. 
     
     
       18. The method of  claim 12 , wherein the exposing step is performed in a manner such that the thin oxide etch resistant layer has sufficient thickness to protect the underlying BOX layer from erosion caused by a subsequent wet cleaning steps. 
     
     
       19. A semiconductor device formed using a wafer comprising a buried oxide (BOX) layer and a semiconductor material layer, the semiconductor device comprising:
 a vertical semiconductor material structure formed overlying the BOX layer; and 
 a thin oxide etch resistant nitride layer formed over an exposed portion of the BOX layer, wherein the thin oxide etch resistant nitride layer is formed to protect a portion of the BOX layer substantially underlying the vertical semiconductor material structure and is adjacent to but not under any portion of the vertical semiconductor material structure. 
 
     
     
       20. The semiconductor device of  claim 19 , further comprising:
 a gate dielectric layer formed around at least a portion of the vertical semiconductor material structure; 
 a gate material structure formed around at least a portion of the gate dielectric layer; 
 a liner formed adjacent the gate material structure, wherein the liner is formed overlying an exposed portion of the thin oxide etch resistant layer; and 
 a spacer formed adjacent the liner.